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About tornadoes

Tornadoes are relatively rare events but they can happen with almost any severe thunderstorm. Of the 10-20 annual sightings in Australia, most are first seen and reported by members of the public. Various methods have been used for estimating maximum wind speeds in tornadoes including time-lapse photography, interpreting damage patterns and theoretical calculations. It is now generally agreed that maximum wind speeds in tornadoes do not exceed 450 km/h.

How and why tornados form

As you can imagine, it requires a narrow range of conditions for a thunderstorm to become tornadic. The key conditions are: an intense, sustained updraught; strong wind shear, i.e. turning and strengthening of the environmental winds with height (e.g. northeast at the surface and northwest aloft); and strong winds at cloud-top level. These conditions allow the thunderstorm's own air-flow pattern to interact with the environmental winds and produce rotation within the updraught.

What it's like near a tornado

Mostly tornadoes occur near the back side of the thunderstorm, near a brightening sky usually to the west. Heavy rain and hail may precede their arrival but once the thunderstorm's main updraught is overhead, only a few scattered hailstones and an eerie calm will accompany their approach. The tornado itself produces a violent wind that begins and ends abruptly. It will last from several seconds to (at most) two minutes and be accompanied by a variety of sounds caused by the damage to buildings, trees, etc. Some people also hear a 'roar' but many tornadoes make no sound at all. If the sound is irregular it is likely the result of damage occurring nearby; but if it is a steady, softer sound that originates in the sky or toward the main thunderstorm cloud, it is more likely caused by large hailstones hitting the ground or colliding in mid-air. After its passage, some light rain or hail can occur, along with cooler winds, before clearing takes place.

The Canberra Times has covered the official launch of ACT First, reporting that, "Too many Canberra residents are failing to take simple steps to safeguard their families and properties against storms and floods."

The Canberra region has experienced an average of one earthquake per year for the past 50 years; and for most residents this information would come as a surprise. Frequency of occurrence of earthquakes within 20 km of Canberra GPO Seventy-two earthquakes occurred within 20 km of the GPO in the 36 years prior to the end of 1995, and during this period yearly numbers varied between zero and nine with a mean number of 2.0.

Flash floods can occur almost anywhere there is a relatively short intense burst of rainfall such as during a thunderstorm. As a result of these events the drainage system has insufficient capacity or time to cope with the downpour. Although flash floods are generally localised, they pose a significant threat because of their unpredictability and normally short duration.

105 people have been killed by landslide events since 1842 in 100 recorded landslide events (National Landslide Database, 2007). Many of these events resulted from natural phenomenon, though half of those causing death and injury can be attributed to human activity.

Green Cross Australia brought a whole new twist to disaster preparedness with a zombie flashmob in Canberra. Zombie-clad locals invaded Canberra’s Old Bus Depot Markets, performing to Michael Jackson’s Thriller – all to support ACT First. See photos of the event on the Canberra Times...

Severe heatwaves were once expected to hit Canberra about once every 25 years, experts say, but the sweltering conditions will be the third such hot spell in the capital in four years.
The Canberra Times reports the blistering heat is a sign of things to come, with the CSIRO predicting ACT residents could suffer through 26 days a year with a top temperature of 35 degrees or more before the end of the century.

A community of ACT social media users will add to front-line preparations this year to prepare Canberrans for their next natural disaster. Read John Thistelton's report from the Canberra Times on the launch of ACT First.

Storms can happen anywhere, but they are more common in the ACT from September to end of February. Severe storms are more common than any other natural hazard and are responsible for more damages measured by insurance costs than bushfires, floods or cyclones.

During a ‘heatwave’ temperatures are above average for several sequential days and it remains hot overnight. Heatwaves have caused more deaths than bushfires in Australia, and cause losses to crops, livestock and infrastructure.

Many people believe that tornados do not occur in Australia; this is not true, they do and have caused numerous deaths. Most thunderstorms do not reach the level of intensity needed to produce these dangerous phenomena, but they all produce lightning which can cause death, injury and damage. Tornados can and do occur in the ACT.